A conventional caster for baggage shown in FIGS. 6 and 7 includes a U-shaped fixing plate 11, an upper plate 12 disposed under and coupled to the fixing plate 11, and a ball bearing 13 fixed under the upper plate 12 by the shaft of a pin 15. An inverted U-shaped hanger which pivotally supports a roller 16 is also fixed to the ball bearing 13 by the pin 15. The fixing plate 11 is secured under a bottom side of a piece of baggage, with the roller 16 standing on the ground to aid the baggage in moving around on the ground.
The conventional caster is found to have the following disadvantages:
1. It does not protrude downward for a large distance, as it is usually made in very small size, and is liable to let a piece of baggage incline or fall down when moved on the ground that is not even or has holes; and, PA1 2. It does not move smoothly on the ground if the baggage is heavily loaded, and is easily damaged.